1. Field of the Invention
The present invention relates to a positioning device for attachment to an extendable member in order to enable a user to easily and accurately position the outermost end of the extendable member adjacent to a desired end position.
2. Description of the Related Art
The accurate positioning of the outermost end of an aerial extension ladder of the type utilized in firefighting vehicles is often difficult because of the considerable distance between the operator who is controlling positioning of the aerial ladder and the outer end of the ladder. At full extension, typical aerial ladders are capable of reaching vertical heights of up to about 110 feet or more, depending upon the particular ladder design. That considerable distance renders it difficult for the operator of the ladder positioning controls to assess how close the outermost end of the extending aerial ladder is relative to its intended destination position. The destination position can be adjacent to a window, to allow entry of a firefighter to a building through the window or to permit the rescue of a person who is at the building window, or it can be the roof of a building. The destination position can also be spaced from a building wall a desired distance to allow a hose nozzle at the end of the ladder to be properly oriented to direct water at the fire at an elevated level. The destination position can also be a position at which an aerial platform is desired to be located.
Because of the difficulty for an aerial ladder operator located at the base of the ladder to assess the position of the outermost end of the extended ladder relative to a desired destination position, another firefighter is often positioned at the base of the structure to act as a spotter. The spotter is spaced from the base of the ladder to visually detect how close the end of the ladder is relative to the wall or structure, and to provide a signal to the ladder operator to enable him to adjust the amount of ladder extension as necessary. Thus, the ladder operator must simultaneously monitor the ladder controls, the position of the outermost end of the ladder, and the instructions provided by the spotter. However, the use of another person on the ground as a spotter, rather than as one fighting the fire, takes from the fire scene a person who could otherwise assist in fighting the fire itself in some other capacity.
There is therefore a need for a device to enable an aerial ladder operator to himself more accurately assess the outermost position of the extended ladder, without the need for a spotter.